I’m curious if anyone happens to have a chart, matrix, or info regarding .308/7.62x51 out of various barrel lengths from a gas gun. More specifically, I’d like to find a comparison in various barrel lengths ranging from 12.5 inches on up to 20+ inches, if possible.
I know there’s a matrix using a Remington 700 chopped down to 16 or 18 inches, but I was really hoping to find more hard data using a short barrel gas gun. I guess what I really liked to see is where the point of diminishing returns is when using a .308 AR.
I would really like to see some form of scientific/properly conducted data on this also.
I seem to recall that previously some reputable sources saying that 21 is excellent, 16 is the short end and 18 is the most practical. Last I chrono’d my 21in FAL with R1M1 it was 2760 (I think:confused:) and my buddy’s 18in was about 2700 and if memory serves me (and it might not) 16in starts to really fall off. Again I’d like to see some empirical data as mine is from long ago and a bit on the Bubbaology side of science:p
I read in a gun rag article reviewing the LWRC REPR that there was only a 50 fps difference between the 16 and 20 inch version of the REPR using M118LR, and 200 fps difference comparing the 12.5 and 16 inch version.
I would love to see a test where a 20" .308 AR has its barrel chopped a couple inches at a time down to 12.5 inches, with the velocity using multiple loads (say M118LR, M80, Mk319, 155gr TAP, 110gr TAP, etc) being recorded at each stage.
I seem to remember a thread at ARFCOM a while back that MSTN had posted from a similar expreiment using an AR-15 using M193, M855, and Mk262. It seems that with a trend moving toward.308 AR carbines in the commercial, LE, and military (the LMT with the UK, the Mk17 with our DoD, etc), this would be some really important info to have.
I have an LTR with a 20" barrrel
my load of 44.5g of Varget, Lapua brass, CCI BR primers and 2.0 with Sierra GK BTSP 165s will put them in the same hole, but I haven’t got around to chronoing the load
So then, It would seem that we are not giving up much by going with a 16" barrel. Only reason for me to get the 18" 5R barrel for my LMTMWS would be for the fact that it is a SS match barrel. Good to know.
I’ve been seeing data here and there that suggested the velocity loss in an AR gas gun was less than 100 fps between the 20" and 16" barrel, but never could find a good breakdown or hard data using the same equipment, ammo, platform, etc. That helps a lot!
I’m really suprised, seeing the minimal velocity loss between the two barrels, and some of the new loads optimized for the shorter barrels (Mk319, 155 Hornady BTHP, etc), that we haven’t seen our DoD follow the path of the MoD and use a 16" barrel for marksman rifles, if not push for an actual battle rifle in the inventory.
I don’t know why, but I get a warm fuzzy thinking about the SR-25EMC or any of the 13.7-16" 30 cal AR’s.
Wow! with those numbers for M118 LR and going by transonic speed the 16" barrel only loses about 80 m of effective range compared to the 20" tubes…
KevinB, what accuracy can you expect at long range with the 16" barrel at 800 m? In this gun, does M118 LR makes it further than supersonic range (with usable accuracy) or not?
moose, can you point a link to where you found the data for the Remington 700? I’m in the process of building a “trunk gun” on a .308 Stevens 200 and am curious what I’d be giving up by chopping the 22" barrel to 18". Was what you found something beyond ballistic tables?
